WO2019229159A1

WO2019229159A1 - Impeller and centrifugal compressor comprising same

Info

Publication number: WO2019229159A1
Application number: PCT/EP2019/064037
Authority: WO
Inventors: Hai Liang TAO; Chen Hui ZHANG; Rui Chun DUAN
Original assignee: Siemens AG; Siemens Corp
Current assignee: Siemens AG; Siemens Corp
Priority date: 2018-05-31
Filing date: 2019-05-29
Publication date: 2019-12-05
Anticipated expiration: 2020-11-30
Also published as: CN208578769U

Abstract

The present utility model relates to an impeller (3), having a wheel disk (31), a wheel cover (32), and a blade (33) located between the wheel disk (31) and the wheel cover (32), wherein at least one anti-rotation plate (34) is disposed on a side, facing away from the blade (33), of at least one of the wheel disk (31) and the wheel cover (32), the anti-rotation blade (34) extending from an outer edge of the impeller (3) toward the center of the impeller (3). The impeller can reduce rotational flow at an inlet of a sealing structure, improve motive power characteristics of a rotor system, and increase the stability of the rotor system. In addition, the present utility model also relates to a centrifugal compressor (1) comprising the impeller (3).

Description

IMPELLER AND CENTRIFUGAL COMPRESSOR COMPRISING SAME

Technical Field

The present utility model relates to an impeller, in particular an impeller for a centrifugal compressor, the impeller having a wheel disk, a wheel cover, and a blade located between the wheel disk and the wheel cover.

In addition, the present utility model also relates to a centrifugal compressor comprising the impeller. The centrifugal compressor is in particular used in the fields of petroleum, petrochemicals and air separation, for supplying nitrogen, oxygen etc. to a downstream zone.

Background art

A centrifugal compressor is a rotary fluid machine having an impeller, mainly comprising a stator and a rotor; the stator is a fixed element of the compressor, and consists of a diffuser, a curved pathway, a back-flow device and a casing, etc.; the rotor mainly consists of elements such as a rotation shaft, the impeller, a balance plate and a thrust plate. When a working medium passes through a centrifugal compressor, the working medium is driven by blades rotating at high speed on the impeller, flows to an edge of the impeller under the action of centrifugal force, and is pressurized in the diffuser. Centrifugal compressors can be classified as single-stage compressors and multi-stage compressors, wherein single-stage compressors are fitted with a single rotor, whereas multi-stage compressors are fitted with multiple rotors connected in series. A sealing structure is installed between a rotating component and a stationary component of a centrifugal compressor, to control leakage flow from a high-pressure zone to a low-pressure zone through a movement gap. The impeller is a key component of a centrifugal compressor. Due to flow-guiding in a cascade channel in the impeller and the rotation of rotating components such as the rotation shaft and a wheel disk, the working medium has a very high circumferential rotational flow speed at an inlet of the sealing structure, causing vibration of a rotor system, and affecting the stability of the rotor system.

Summary of the utility model

An object of the present utility model is to provide an impeller, in particular an impeller for a centrifugal compressor, which is capable of reducing rotational flow at an inlet of a sealing structure, improving motive power characteristics of a rotor system, and increasing the stability of the rotor system.

The abovementioned object is achieved by means of an impeller, in particular an impeller for a centrifugal compressor, according to the present utility model; the impeller has a wheel disk, a wheel cover, and a blade located between the wheel disk and the wheel cover, wherein at least one anti rotation plate is disposed on a side, facing away from the blade, of at least one of the wheel disk and the wheel cover, the anti-rotation blade extending from an outer edge of the impeller toward the center of the impeller. The impeller can thereby stop uniform flow of a gas stream in a circumferential direction when the impeller is rotating at high speed, and in turn stop aerodynamic rotational flow entering a rotation shaft seal, thereby achieving the effect of stopping rotation and inhibiting vibration.

Advantageously, the anti-rotation plate may extend substantially in a radial direction of the impeller. Due to the presence of the anti-rotation plate, a working medium will be forced to flow in a radial direction under the action of a centrifugal force generated by high-speed rotation. Uniform flow of a gas stream in a circumferential direction when the impeller is rotating at high speed can be stopped, achieving the effect of stopping rotation and inhibiting vibration. In addition, a pressure distribution at the back of the wheel disk or wheel cover can be adjusted, thereby achieving the objective of reducing single-stage impeller axial force, and the balance piston that is generally used in the prior art can be omitted, such that the rotation shaft length is reduced, further increasing rotor stability. At the same time, a form of pressure distribution can be realized in which a back cavity pressure gradually increases from the vicinity of the shaft to the outer edge of the impeller; this is highly advantageous for the design of sealing at the rotation shaft, and at the same time lowers the pressure in the vicinity of the shaft, so can reduce the amount of leakage at a rotation shaft seal.

According to a preferred embodiment of the present utility model, a height of the anti-rotation plate in an axial direction of the impeller may gradually decrease from the outer edge of the impeller toward the center of the impeller. In this way, it is possible to realize a desired form of distribution of pressure which gradually increases from the vicinity of the shaft to the outer edge of the impeller in a back cavity of the impeller .

According to a preferred embodiment of the present utility model, multiple anti-rotation plates may be provided to form a cascade, the quantity of the anti-rotation plates being such that the cascade has a solidity greater than 1. The anti rotation plates are for example in the form of blades, and the cascade is formed by arranging multiple blades having the same blade profile, at the same separation and angle, on the same surface of revolution, e.g. on the wheel disk or wheel cover. When the cascade solidity is greater than 1, the level of leakage caused by high-speed rotation of the impeller is very low .

According to a preferred embodiment of the present utility model, a length of the anti-rotation plate may be set according to a back cavity pressure of the impeller. By adjusting the length of the anti-rotation plate, pressure in a back cavity of the impeller can be adjusted.

According to a preferred embodiment of the present utility model, a height of the anti-rotation plate in an axial direction of the impeller may also be adjusted according to a gap between the impeller and a fixing element, with the impeller being disposed in the fixing element. In this way, leakage is reduced as much as possible.

According to a preferred embodiment of the present utility model, a thickness of the anti-rotation plate is set according to a strength design standard, such that the anti-rotation plate is able to bear pressure caused by the working medium when the impeller is rotating at high speed.

According to a preferred embodiment of the present utility model, the anti-rotation plate may have the shape of a straight line, a conic section or a spline curve.

According to a preferred embodiment of the present utility model, the anti-rotation plate and two blades adjacent thereto between the wheel disk and the wheel cover are arranged so as to be staggered by a certain angle. More preferably, the anti rotation plate is disposed in a middle position between the two blades. Since the wheel disk or wheel cover is generally thin, the strength of the wheel disk or wheel cover can be increased by disposing the anti-rotation plate between two blades, producing the effect of a reinforcing rib. Thus, the wheel disk or wheel cover can be designed to be thinner, and the strength of the impeller can be maintained while reducing the mass of the impeller.

According to a preferred embodiment of the present utility model, the anti-rotation plate is formed by milling integrally with at least one of the wheel disk and the wheel cover. Thus, an impeller with an anti-rotation plate can be manufactured simply at a low cost.

According to another aspect of the present utility model, a centrifugal compressor is also provided, comprising at least one impeller as described in any one of the embodiments above. The centrifugal compressor has the advantages described in relation to the impeller above.

Preferably, in the case where the centrifugal compressor comprises multiple stages of impellers, each impeller may be designed as an impeller as described in any one of the embodiments above. Alternatively, only an impeller in a final stage or impellers in final stages may be constructed according to any one of the embodiments above, because the impeller in the final stage or the impellers in the final stages bear the greatest pressure.

Brief Description of the Drawings

The abovementioned characteristics, technical features and advantages of the present utility model and embodiments thereof are explained further below in a clear and easy-to-understand way by explaining preferred embodiments, with reference to the accompanying drawings, wherein:

Fig. 1 shows schematically an axial sectional view of a known centrifugal compressor in the prior art. Fig. 2 shows schematically a partial sectional view of an impeller according to a preferred embodiment of the present utility model.

Figs. 3 and 4 show schematically a three-dimensional view and a side view respectively of the impeller shown in fig. 2.

Fig. 5 shows schematically an axial sectional view of a centrifugal compressor having the impeller shown in fig. 2.

In the drawings, identical or functionally identical components are indicated by identical reference labels; similar or functionally similar components are indicated by similar reference labels.

Detailed Description of Embodiments

The design of a known centrifugal compressor in the prior art is as shown in fig. 1; multiple impellers 3 are mounted on a rotation shaft 2 of the centrifugal compressor 1, and sealing structures 5 are mounted between rotating components of the centrifugal compressor on the one hand and stationary components on the other. At one end of the rotation shaft 2 of the centrifugal compressor, a balance piston mechanism 6 is mounted by thermal shrinkage, and axial thrust is adjusted by changing the piston diameter and pressure difference at two sides of the balance piston 6.

Fig. 2 shows a partial sectional view of an impeller according to a preferred embodiment of the present utility model. The impeller 3 has a wheel disk 31, a wheel cover 32, and blades 33 located between the wheel disk 31 and the wheel cover 32. In the preferred embodiment shown in fig. 2, multiple anti rotation plates 34 are disposed on a side of the wheel disk 31 facing away from the blades 33. The anti-rotation plates 34 extend substantially in a radial direction of the impeller. The anti-rotation plates 34 are formed by milling integrally with the wheel disk 31.

A height h by which the anti-rotation plates 34 extend from the side of the wheel disk 31 in an axial direction of the impeller gradually decreases from an outer edge of the impeller toward the center of the impeller, thereby realizing a desired form of distribution of pressure p which gradually increases from the vicinity of the shaft to the outer edge of the impeller in a back cavity 7 of the impeller. The height h of the anti rotation plates 34 in the axial direction of the impeller may also be adjusted according to a gap between the impeller 3 and an inner wall of a fixed element 4 as shown in fig. 1, so that leakage is reduced as much as possible.

It can be seen more clearly in the three-dimensional view shown in fig. 3 and the side view shown in fig. 4 that multiple anti rotation plates 34 are provided to form a cascade; the anti rotation plates 34 are curved, extending along a curved line from an end close to the shaft toward an impeller edge end.

Here, the quantity of the anti-rotation plates 34 is such that the cascade solidity is greater than 1. Cascade solidity is the ratio of blade profile chord length to cascade pitch, i.e.

o=s/t

in the above expression: s denotes solidity; s denotes blade profile chord length, i.e. the distance between the two endpoints of the mean camber line of the blade profile; t denotes cascade pitch, wherein the cascade pitch t is obtained via the following expression:

t=2nrm/Zn

wherein rm denotes the mean radius of the back blades on the impeller, and Zn denotes the quantity of anti-rotation plates.

When the solidity is greater than 1, the level of leakage caused by high-speed rotation of the impeller is very low. A length 1 of the anti-rotation plates 34 can be adjusted according to pressure in the back cavity 7 of the impeller. By adjusting the length 1 of the anti-rotation plates, pressure in the back cavity of the impeller can be adjusted. The longer the length of the anti-rotation plates, the lower the pressure in the back cavity.

A thickness of the anti-rotation plates 34 in a circumferential direction is set according to a strength design standard, such that the anti-rotation plates 34 are able to bear pressure caused by the working medium when the impeller is rotating at high speed.

Each anti-rotation plate 34 is disposed in a middle position between two blades 33 adjacent to the anti-rotation plate. The strength of the wheel disk can thereby be increased, producing the effect of reinforcing ribs.

Fig. 5 shows an axial sectional view of a centrifugal compressor having the impeller shown in fig. 2. The centrifugal compressor has multiple impellers 3 as shown in fig. 2. Rotational flow at an inlet of the sealing structure 5 can be reduced, the motive power characteristics of the rotor system of the centrifugal compressor can be improved, and stability is increased. In addition, since the pressure in the back cavity 7 of the impeller is significantly reduced, the balance piston 6 can be omitted in this case, so the length of the rotation shaft 2 can be reduced, and the stability of the rotor system of the centrifugal compressor is further increased.

The present utility model has been presented and explained in detail above by means of the accompanying drawings and preferred embodiments; however, the present utility model is not limited to the disclosed embodiments, and other solutions derived therefrom by those skilled in the art shall also be included in the scope of protection of the present utility model .

Claims

1. An impeller (3), having a wheel disk (31), a wheel cover (32), and a blade (33) located between the wheel disk (31) and the wheel cover (32), characterized in that

at least one anti-rotation plate (34) is disposed on a side, facing away from the blade (33) , of at least one of the wheel disk (31) and the wheel cover (32), wherein the anti-rotation blade (34) extends from an outer edge of the impeller (3) toward the center of the impeller (3) .

2. The impeller (3) as claimed in claim 1, characterized in that a height of the anti-rotation plate (34) in an axial direction of the impeller gradually decreases from the outer edge of the impeller (3) toward the center of the impeller (3) .

3. The impeller (3) as claimed in claim 1 or 2, characterized in that multiple anti-rotation plates (34) are provided to form a cascade, the quantity of the anti-rotation plates (34) being such that the cascade has a solidity greater than 1.

4. The impeller (3) as claimed in claim 1 or 2, characterized in that a length of the anti-rotation plate (34) is set according to a back cavity pressure of the impeller (3) .

5. The impeller (3) as claimed in claim 1 or 2, characterized in that a height of the anti-rotation plate (34) in an axial direction of the impeller is adjusted according to a gap between the impeller (3) and a fixing element (4), with the impeller (3) being disposed in the fixing element (4) .

6. The impeller (3) as claimed in claim 1 or 2, characterized in that a thickness of the anti-rotation plate (34) in a circumferential direction of the impeller is set according to a strength design standard.

7. The impeller (3) as claimed in claim 1 or 2, characterized in that the anti-rotation plate (34) has the shape of a straight line, a conic section or a spline curve.

8. The impeller (3) as claimed in claim 1 or 2, characterized in that the anti-rotation plate (34) and two blades (33) adjacent thereto between the wheel disk (31) and the wheel cover (32) are arranged so as to be staggered by a certain angle .

9. The impeller (3) as claimed in claim 8, characterized in that the anti-rotation plate (34) is disposed in a middle position between the two blades (33) .

10. The impeller (3) as claimed in claim 1 or 2, characterized in that the anti-rotation plate (34) is formed by milling integrally with at least one of the wheel disk (31) and the wheel cover (32) .

11. A centrifugal compressor (1), comprising at least one impeller (3) as claimed in any one of claims 1 - 10.